You mentioned you like "slow and emotional pieces." You should check out Chopin's Nocturnes. They are all amazing romantic solo piano piano pieces that are definetly "slow and emotional."
For more solo piano I would start out with the Beethoven sonatas and Bach's Well Tempered Klavier.
I play the piano, so I love listening to piano works. But if you aren't into it you should check out Beethoven's symphonies and string quartets especially the late ones. I would say that his String Quartet in C# minor, Op. 131 is one of the most powerful pieces I know.
I guess that will get you started. If you like the Chopin a lot look into more composers from the Romantic period like Liszt, Shumann, Tchaikovsky. And If you like the Beethoven, look into Schubert and Mozart as well.
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